JPH0617941B2 - Color imaging device - Google Patents

Description

The present invention relates to a color image pickup device, and more particularly to a color image pickup device of a frame sequential image pickup system.

[Prior Art] As a conventional example of a frame-sequential color image pickup device, a solid-state image pickup device is built in at the tip of an endoscope, and illumination light is sequentially red-lighted every frame.
There is an endoscope image pickup apparatus that sequentially colors the R, G, and B component images by coloring in (R), green (G), and blue (B). The solid-state image pickup device built in the tip of the endoscope is most required to be downsized. Therefore, unlike a normal image pickup device, there is no light-shielding portion for reading and scanning, and only a light-receiving portion. Therefore, it is necessary to shield the solid-state imaging device from light when reading out, and when coloring the illumination light that illuminates the inside of the body cavity, a light-shielding period is provided after the coloring period of each frame. Therefore, not all the illumination light emitted from the lamp is emitted, and the utilization efficiency of the illumination light is poor. Since the deterioration of the illumination light leads to the deterioration of the image quality, it is conceivable to set the light emission amount of the lamp to be considerably high. However, when the lamp emits a large amount of light, it has a short life and requires a large cooling device for preventing heat generation of the lamp. Therefore, it is conceivable to control the lamp so that the light amount is reduced or reduced to zero during the light-shielding period and the light amount is increased only during the coloring period, rather than always emitting a large amount of light. However, it is not preferable from the viewpoint of life that the lamp is frequently turned on / off or the amount of light is changed.

[Problems to be Solved by the Invention] As described above, the conventional frame-sequential imaging type color imaging device has a problem that the illumination light emitted from the light source is not effectively used.

The present invention has been made in view of such a problem, and provides a color image pickup apparatus capable of illuminating a subject with a large amount of light without shortening the life of a lamp and obtaining a good image quality. The purpose is to

[Means for Solving the Problems] According to the present invention, in a color image pickup apparatus of a field sequential image pickup system that sequentially illuminates a subject with illumination light of different color components and picks up an image for each color component. A light emission control unit that increases the light amount of the illumination light during the image pickup period, an amplification unit with a variable amplification factor that is supplied with an image pickup signal, and the amplification unit during the image pickup period of the specific color component where the light amount of the illumination light is increased. And an amplification factor control means for reducing the amplification factor.

[Operation] In this device, the light amount of the illumination light is increased only during the image pickup period of the specific color component, and at this time, the amplification factor of the amplification means for amplifying the image pickup signal is correspondingly reduced, so that the life of the lamp is shortened. The illumination light can be effectively used and the image quality can be improved.

[Embodiment] An embodiment of a color image pickup apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of this embodiment. Here, instead of providing an image guide, a solid-state image pickup device is built in at the tip of the endoscope, an image of a subject is picked up, and an image pickup signal is supplied to an external monitor via the endoscope to display it. Will be described as an embodiment applied to the. The light source unit 12 is connected to the endoscope body 10. The light source unit 12 has a signal processing function of processing an image pickup signal in addition to a normal light source function. The endoscope body 10 has a CCD 14 as a solid-state image sensor at the tip. Further, the endoscope body 10 includes a light guide 1 formed of an optical fiber that transmits the illumination light from the light source unit 12 to the tip thereof in order to illuminate the subject with the illumination light from the light source unit 12.
Have six. The light source unit 12 includes a lamp 18, and illumination light emitted from the light source unit 12 is incident on one end of the light guide 16 via relay lenses 20 and 22. A rotary color filter 24 having three color filter components of red (R), green (G), and blue (B) is provided between the relay lenses 20 and 22. The rotary color filter 24 is rotated by a motor 26, and rotation control is performed so that the illumination light incident on the light guide 16 is sequentially colored into R, G, and B in each frame imaging period of the CCD 14.

A plan view of the rotary color filter 24 is shown in FIG. As described above, since the CCD 14 is not provided with the light-shielding portion for read-out scanning, the rotary color filter 24 has filter components 24a, 24b, 24 for R, G, B colors.
A light shielding part is provided between c. While the filter components 24a, 24b, 24c of the respective colors color the illumination light from the lamp 18, the CCD 14 captures a subject image of the respective color components, and while the light shielding unit shields the illumination light from the lamp 18, the CCD 14 The image pickup signal is read from. CCD14
The signal read from the light source unit 12 is supplied to the light source unit 12,
It is input to the video signal processing circuit 30. Further, the rotary color filter 24 is provided with position detection marks 28a, 28b, 28c indicating the start positions of the filter components of the respective colors. These marks 28a, 28b, 28c are the detectors 3 provided on the periphery of the rotary color filter 24.
Detected by 2. The output signal of the detector 32 is input to the video signal processing circuit 30 and is also supplied to the lighting control circuit 34. The output of the lighting control circuit 34 is supplied to the lamp lighting circuit 36, and the light emission of the lamp 18 is controlled.
The output of the video signal processing circuit 30 is displayed on the color monitor 38.

A detailed circuit diagram of the video signal processing circuit 30 is shown in FIG.
Image pickup signal from CCD 14 is sample hold (SH)
It is input to the variable amplification factor amplifier 54 via the circuit 50 and the clamp circuit 52. The amplification factor of the variable amplification factor amplifier 54 is controlled according to the output signal of the detector 32. The output signal of the variable amplification factor amplifier 54 is passed through the A / D converter 56 and the multiplexer 58 to generate frame memories 60a, 60b, 60c.
Stored in. The switching of the multiplexer 58 is also the detector 3
The R, G, and B component signals are stored in the frame memories 60a, 60b, and 60c, respectively. The R, G, B signals read from the frame memories 60a, 60b, 60c are converted into D / A converters 62a, 6a.
2b, 62c to the outside, the color monitor 3
It is displayed at 8.

Next, the operation of this embodiment will be described with reference to FIG.
When the power is turned on, the motor 26 is rotated at a constant speed, and the detector 32 outputs a rotation detection pulse having a constant period as shown in FIG. 4 (a). When the rotary color filter 24 is rotated by the motor 26, the illumination light emitted from the lamp 18 has a light-shielding period between each coloring period as shown in FIG. B is colored.
As shown in FIG. 4 (c), the CCD 14 is in the accumulation period during the period in which the subject is illuminated with the illumination light of each of the R, G, and B color components, and the CCD 14 is in the readout period during the illumination light blocking period. Lighting of the lamp 18 is controlled by a current from the lamp lighting circuit 36. The lighting control circuit 34 supplies a semi-flash signal to the lamp lighting circuit 36 in response to the rotation detection pulse output from the detector 32 during the period when G-color illumination light is emitted as shown in FIG. 4 (e). To do. Lamp lighting circuit 3
6 normally supplies the lamp drive current of 18 A to the lamp 18, and increases the lamp drive current to 27 A as shown in FIG. 4 (f) in response to this semi-flash signal. As a result, the amount of light emitted from the lamp 18 is increased during the period in which the G-color illumination light is emitted as compared with the other periods.

On the other hand, the output signal of the CCD 14 is SH as shown in FIG.
The signal is amplified by the variable amplification factor amplifier 54 via the circuit 50 and the clamp circuit 52. The amplification factor of this amplifier 54 is shown in FIG.
As shown in (d), the period during which the amount of light emitted from the lamp 18 is increased, that is, the period during which the G-color illumination light is emitted, is shorter than the other periods. / 1.
It is reduced by 5 times.

As described above, since the image of the G color component is imaged under the illumination of a large amount of light with respect to the R and B color component images, the resolution is improved. This is because the noise of the image pickup signal can be reduced by increasing the amount of illumination light. The resolution of the entire color image largely depends on the resolution of the luminance component,
Since the resolution of the image of the G color component that affects the luminance signal is improved, the resolution of the entire color image is also improved according to this embodiment. In addition, the level of the image pickup signal from the CCD 14 increases during the G illumination period as compared with other periods, but the amplification factor of the amplifier 54 that amplifies the image pickup signal decreases, so
The level will not extremely increase with respect to the image pickup signals of other color components, and the color balance will not be lost.

Further, according to this embodiment, since the light emission amount of the lamp 18 is increased only when the G color component is illuminated, the lamp 1 is increased as compared with the conventional case where the light intensity is increased each time when each color is illuminated.
8 life is extended. FIG. 5 shows the relationship between the brightness and the life of the lamp 18 when it is turned on. In this embodiment, the solid line in FIG. 5 sets the lamp drive current to 18 A during normal operation and 27 A during G color illumination. The broken line indicates that the lamp drive current is fixed at 18 A. It is a characteristic when it is kept constant.

It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made. The amount of light emitted from the lamp 18 may be increased not when the G color is illuminated, but when the other color is illuminated. For example, in the stomach and the like, the red component is much larger than the other components. for that reason,
When capturing an image of the stomach or the like, the overall resolution is improved even if the amount of light is increased during illumination of R and noise in the image signal of the R component is reduced. Further, the solid-state image pickup device is not limited to the CCD and may be another device, and the lamp drive current and the amplification factor of the amplifier 54 are not limited to the above values.

As described above, according to the present invention, the light amount of the illumination light is increased only during the image pickup period of the specific color component, and at this time, the amplification factor of the amplification means for amplifying the image pickup signal is correspondingly decreased. Therefore, it is possible to provide a color image pickup device in which the illumination light can be effectively used and the image quality is improved without shortening the life of the lamp.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a color image pickup device according to the present invention, FIG. 2 is a plan view of a rotary color filter in FIG. 1, and FIG. 3 is a video signal processing circuit in FIG. FIG. 4 (a) to FIG. 4 (f) are timing charts for explaining the operation of this embodiment, and FIG. 5 is a characteristic diagram showing the life of the lighting-controlled lamp according to this embodiment in comparison with the conventional example. It is a figure. 14 ... Solid-state image sensor 18 ... Lamp 24 ... Rotating color filter 26 ... Motor 30 ... Video signal processing circuit 54 ... Variable amplification factor amplifier

Claims (1)

[Claims] 1. A color image pickup apparatus of a frame-sequential image pickup system which sequentially illuminates an object with illumination light of different color components and picks up an image for each color component, and emits light for increasing the amount of illumination light during an image pickup period of a specific color component. A control unit, an amplification factor variable amplification unit to which an imaging signal is supplied, and an amplification factor control unit that lowers the amplification factor of the amplification unit during an imaging period of the specific color component in which the light amount of the illumination light is increased. A color image pickup device comprising: